Chopjock,
If this "incident" had occurred in the air it would be an "accdient" for sure.
It is an interesting question you pose about the forces....but I would imagine hovering cross wind in a very strong wind at max weight would also produce quite a bit of force. Whether making tight turns on the ground....or forgetting the nose wheel lock and trying to make a turn would exceed the airborne forces is for the design engineers to answer to.
No matter.....tail booms are not supposed to fail this way for any reason shy of a massive overloading such as a tail boom strike or crash. (IMHO anyway!)